Most of San Diego County will escape the worst of a heat wave gripping Southern California this week. The desert? Not so lucky.

Borrego Springs is forecast to reach 119 degrees today and 117 Wednesday. Both would set records for the date. And little relief will occur at night, when the lows are not expected to dip below the mid-80s.

Those kinds of temperatures, even in the desert where the high this time of year is normally about 107, have brought an excessive heat warning from the National Weather Service.

Forecasters are cautioning people who must be outside to wear light and loose-fitting clothing, drink plenty of fluids, schedule strenuous outdoor activities for the morning or evening, and watch for signs of heat exhaustion or heat stroke.

Borrego Springs resident Sid Engel said it was a tolerable 112 at his home Monday afternoon, and 111 on Sunday. Other thermometers in town Monday were reading 115 and 113.

“But it’s been dry,” he said. “There’s no humidity with it, so it’s not too bad.”

The San Diego County mountains also will be hot and dry, with highs near 90.

Local Cal Fire Chief Kelly Zombro issued a “no burn” proclamation for the area “due to the extreme menace of destruction by fire” because of the weather conditions.

The order means all burn permits issued in Cal Fire’s jurisdiction are suspended until further notice, and campfires are allowed only in established campground rings open to the public. The order does not apply to incorporated cities.

Areas west of the mountains will have a marine layer that should keep the coast mostly in the upper 70s, while the inland valleys will see the high 80s or low 90s — fairly typical for July. Foothill locations, including Ramona and Alpine, should be a few degrees warmer.

Dry conditions should be less of a problem Wednesday when monsoonal moisture arrives from the east and southeast, bringing a chance of thunderstorms to the mountains and deserts.

Engel, 84, doesn’t look forward to the steamy weather.

“Humidity makes it hard to breathe when it’s that hot,” he said. “Especially when the breeze comes from the Salton Sea, it’s not nice. It’s humid, and it smells.”